For a determining of centering data for eyeglasses it is necessary to know the viewing direction of the test person. This can be effected by specification of a fixation object about which further information is known in advance or can be determined, such as, for example, the nasal root method with ImpressionIST, an additional reference object as disclosed in U.S. Pat. No. 7,909,460 B1, or virtually at infinitely distant points.
In addition, the individual data can comprise a position/a diameter of a pupil that is measured in the same situation and is used for optimizing the glasses based on average HOAs, as disclosed in WO 2013/087 212 A1.
However, the common methods detect the pupil quite imprecisely or determine the pupil diameter quite imprecisely.
Furthermore, the measuring of various individual parameters is made possible by different device classes. Thus there are pupillometers for measuring pupil diameters, eye trackers that make possible a viewing-direction measurement, and video-centering systems that determine centering data.
The two first-mentioned device classes are generally used under laboratory conditions, wherein limitations such as head-fixing, absence of ambient light, lack of flexibility due to cable connections, and components to be applied to the test person are accepted. In addition, an absolute measurement is often not necessary, but rather a relative measurement is sufficient, such as, for example a pupil-diameter reaction to light pulses. In addition, with eye tracking, lighting systems are often used whose reflection on the eye is analyzed. For video centering, in determining the pupil diameter the view is usually set to infinity. Since it is usually not possible to attach a fixing object at infinity, devices are required that either image an object at infinity or a correction is performed that, with the view of a known object positioned at a finite distance, can determine the difference to the pupil diameter with the view at infinity. However, an eye model can also be used for this purpose; in particular the eye length is relevant therefor. For this purpose the eye/fixing-object distance is required. With ImpressionIST from Rodenstock, the nasal root of the mirror image of the customer is used as fixing object.
It would therefore be desirable to provide a possibility by which the pupil diameter can be determined with higher precision without requiring information about a fixing object in a video centering, thus making it possible to precisely determine a pupil diameter in an ordinary environment.
It is therefore the goal of the invention to propose a possibility that avoids or at least reduces at least a part of the disadvantages known in the prior art.